For example, they say, “It needs to handle 500 connections/second.” Don’t let them say “users”, “users” means nothing. Then you go test their current WizBangOMatic and find it only handles 10 conn/second. You can then come to them and say that Rails can’t do 500 conn/second, but it can do better than the WizBangOMatic which only has 10 conn/second performance. It’s evil, but it puts the performance harpies at rest.